## **Core Concept**
Anaemia associated with chronic diseases, including pulmonary tuberculosis (TB), is a common finding. This type of anaemia is typically caused by chronic inflammation. The underlying mechanism involves the effect of cytokines on iron metabolism and erythropoiesis.

## **Why the Correct Answer is Right**
The correct answer, **C. Anaemia of chronic disease**, is right because pulmonary TB is a chronic infectious disease that leads to a sustained inflammatory response. This chronic inflammation results in the production of cytokines such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha). These cytokines affect the production and utilization of iron and erythropoietin, leading to a decrease in the availability of iron for erythropoiesis and a relative deficiency of erythropoietin, which together cause a normocytic or microcytic anaemia.

## **Why Each Wrong Option is Incorrect**
- **Option A: Pernicious anaemia** is incorrect because it is caused by a deficiency in vitamin B12 due to the lack of intrinsic factor, often resulting from autoimmune gastritis, and is not directly related to pulmonary TB.
- **Option B: Sideroblastic anaemia** is incorrect because it is a group of disorders characterized by the accumulation of iron in the mitochondria of red blood cell precursors, often due to genetic mutations or acquired conditions like myelodysplastic syndromes, and is not directly linked to TB.
- **Option D: Iron deficiency anaemia** is incorrect in this context because, although iron deficiency can cause anaemia, the primary issue in TB-related anaemia is not a lack of iron but rather the body's inability to utilize iron effectively due to chronic inflammation.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that anaemia of chronic disease is often normocytic and normochromic, and it can be differentiated from iron deficiency anaemia by the presence of adequate or increased iron stores in the bone marrow and by elevated levels of ferritin, which reflects the body's iron stores.

## **Correct Answer: C. Anaemia of chronic disease**